Some log messages in the puma log are not structured

We are seeing

I, [2020-02-12T08:11:40.441973 #28720]  INFO -- omniauth: (google_oauth2) Callback phase initiated.

mixed with structured logs which is causing these unstructured messages to be dropped by central logging.

example:

{"timestamp":"2020-02-12T08:09:16.162Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17797.63671875 mb with master and 16 workers."}
I, [2020-02-12T08:09:19.871323 #26170]  INFO -- omniauth: (github) Request phase initiated.
I, [2020-02-12T08:09:27.320688 #29991]  INFO -- omniauth: (github) Request phase initiated.
{"timestamp":"2020-02-12T08:09:36.163Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17793.5 mb with master and 16 workers."}
{"timestamp":"2020-02-12T08:09:56.165Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17772.97265625 mb with master and 16 workers."}
{"timestamp":"2020-02-12T08:10:16.167Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17859.33984375 mb with master and 16 workers."}
{"timestamp":"2020-02-12T08:10:36.168Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17744.82421875 mb with master and 16 workers."}
I, [2020-02-12T08:10:48.857154 #26170]  INFO -- omniauth: (google_oauth2) Request phase initiated.
{"timestamp":"2020-02-12T08:10:56.171Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17652.68359375 mb with master and 16 workers."}
I, [2020-02-12T08:11:07.757601 #30414]  INFO -- omniauth: (github) Request phase initiated.
{"timestamp":"2020-02-12T08:11:16.172Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17738.0546875 mb with master and 16 workers."}
{"timestamp":"2020-02-12T08:11:36.174Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17872.3671875 mb with master and 16 workers."}
I, [2020-02-12T08:11:40.441973 #28720]  INFO -- omniauth: (google_oauth2) Callback phase initiated.
{"timestamp":"2020-02-12T08:11:56.176Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17776.74609375 mb with master and 16 workers."}
I, [2020-02-12T08:12:00.355857 #30414]  INFO -- omniauth: (google_oauth2) Request phase initiated.
{"timestamp":"2020-02-12T08:12:16.177Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17722.09765625 mb with master and 16 workers."}
{"timestamp":"2020-02-12T08:12:36.179Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17828.9375 mb with master and 16 workers."}
{"timestamp":"2020-02-12T08:12:56.181Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17798.52734375 mb with master and 16 workers."}
I, [2020-02-12T08:13:12.606189 #25750]  INFO -- omniauth: (github) Request phase initiated.
{"timestamp":"2020-02-12T08:13:16.183Z","pid":10374,"message":"PumaWorkerKiller: Consuming 17823.328125 mb with master and 16 workers."}

!21101 (merged) was the change for json formatting, @qzhaogitlab can you think of why these logs would be coming through without json formatting in puma_stdout.log?